Food allergies, of which the first to occur in life is most often cow's milk allergy, are caused, in most cases, by a reaction to proteins in food. Various cow's milk proteins, e.g. β-lactoglobulin, casein, α-lactalbumin and serum albumin have been identified as allergens (Wal, J. M. (1998) Cow's milk allergens, Allergy, 53, 1013-1022). Also proteins derived from cow's milk, such as caseinate have been identified as allergens.
In the early years of life the human immune system is still developing and may fail to develop (oral) tolerance to dietary antigens. The result is that a human subject, such as a baby or child mounts an exaggerated immune response to the dietary protein and develops an allergic response to it.
Most often, food hypersensitivity develops just after a susceptible baby or child first encounters a new food containing potential allergens. Apart from its mother's milk, the first dietary proteins generally encountered by human babies are cow's milk proteins and, as noted above, cow's milk allergy is the most common food allergy in human babies. It is generally accepted that babies with established cow's milk allergy also have an increased risk of developing allergies to other dietary proteins such as egg and cereal proteins. All these allergies may manifest themselves clinically as atopic diseases such as atopic dermatitis, intestinal problems, eczema and asthma. Hence, a need exists to prevent or treat such allergies.
Without the intention to be bound by any theory it is believed that, food derived proteins are in persons susceptible to food allergy responsible for the induction of type 1(acute)-hypersensitivity reactions after initial sensitization. Type 1 allergic reactions to food proteins leading to food allergy are characterized in majority by T helper 2 (Th2) polarization of the immune response resulting in the production of allergen-specific IgE (sensitization phase).
Binding of IgE to the high affinity receptor FcsεR1 on mast cells and basophils followed by subsequent cross-linking of the receptors by the specific allergen provokes degranulation (effector/challenge phase). The release of mediators such as histamine, leukotriens and cytokines results in clinical symptoms involving the skin, gastrointestinal tract, airways and sometimes anaphylaxis within a few minutes to one hour after ingestion of the specific food.
From a dietary point of view a need thus exists to prevent the development of an allergy against milk proteins, such as cow's milk proteins. This is of importance because very often cow's milk or milk from other mammals is used to supplement or completely replace human breast milk fed to babies.
In general, postponing the contact with intact milk protein prevent subjects from developing an allergy against milk proteins, such as cow's milk proteins. Basically, there are two ways to postpone the contact with intact milk protein.
The first way is to completely avoid foods containing milk proteins. However, such diets have the disadvantage that compliance is low because available foodstuffs are very restricted. Moreover, for infants, cow's milk protein-based formula have been determined as the best alternative for human breastmilk.
A second way to prevent the development of an allergy against milk proteins is to alter the allergenic properties of the milk proteins by hiding, destroying or disclosing allergic epitopes through conformational changes in proteins, or by improving the access of the hidden epitopes located within the protein to the gastrointestinal enzymes (Guo et al., (1995), Susceptibility of ε-lactoglobulin and sodium caseinate to proteolysis by pepsin and trypsin., Journal of Dairy Science, 78, 2336-244).
One commonly applied method is to extensively hydrolyse the (potential) allergenic food proteins. However, most often these kinds of products have a poor taste and poor functional properties, such as insolubility, impaired emulsification capacity, and/or poor rheological properties. Moreover, by extensive hydrolysis, these proteins may lose their capability to induce oral tolerance. This means that the subject will still be sensitive to develop an allergy when it ingests the intact protein.
Another way of preventing a food allergy is to induce oral tolerance by way of administering over a period of several weeks relatively small amounts of the allergenic protein, such as cow's milk proteins, to human subjects. It may also be possible to administer the allergenic protein to subjects at risk of developing allergy in (slightly) changed form. For this purpose (partially) hydrolyzed proteins are used.
In Fritsché et al. (J. Allergy Clin. Immunol, Vol 100, No. 2, pages 266-273, 1997) it is shown in animal models that the usage of enzymatically hydrolysed milk proteins with a degree of hydrolysis of 18% were able to induce oral tolerance to intact cow's milk proteins. Results of these experiments showed that feeding of rats with such hydrolysed cow's milk proteins, whose allergenicity had been reduced over 100 times as compared to untreated proteins, suppressed the allergic reaction.
Also in van Esch et al. (Pedriatic allergy and immunology, 2011:22:820-826) it has been shown that whey protein hydrolysates have the capacity to induce oral tolerance to whey.
However, as already indicated above, the enzymatic hydrolysis of food proteins, in particularly cow's milk proteins, causes a poor taste and poor functional and/or rheological properties, which is particularly the case with food products wherein the casein is hydrolyzed. Such a poor taste and lack of good functional and/or rheological properties has to be masked with other ingredients, which further increases the costs and complexity of the process and the product.
Another way of lowering the antigenicity of food proteins is to polymerize or cross-link these proteins (Clare, D. A. et al., 2007, Transglutaminase polymerization of peanut proteins. Journal of Agriculture and Food Chemistry, 55, 432-438.).
In a study of Villas-Boas et al. the effect of transglutaminase induced polymerization on the antigenicity of β-lactoglobulin has been examined (Villas-Boas, M. B., et al. 2010, The effect of transglutaminase-induced polymerization in the presence of cysteine on β-lactoglobulin antigenicity, International Dairy Journal, 20, 6, pp 386-392.). In this study additional agents, such as cysteine, had to be used in order to be able to treat the β-lactoglobulin with transglutaminase. Moreover, it was shown that the pepsin digestion carried out of the polymerized samples did not suppress the antigenicity of β-lactoglobulin.
In the article of Stanic et al., in Mol. Nutr. Food Res. 2010., the cross-linking of casein by means of an enzymatic treatment has been described. However, in this article only subjects have been examined which had already developed an allergy against casein. Stanic et al., is silent about the non-sensitizing ability of the cross-linked caseins and does not describe the prevention of the development of an allergy against casein, nor does it describe to potential of the cross-linked casein or caseinate to induce oral tolerance.
An important milk protein present in milk is casein. Casein constitutes about 80% of the proteins in cow's milk and between 20 and 45% in human milk.
In view of the relatively high content of casein in milk (e.g cow's milk) or milk products, an allergy against this protein, its salts (caseinates) or derivates may cause considerable problems. Hence, a serious need exists to prevent allergies against these proteins, and to induce oral tolerance against them.